World's First Tooth Regrowth Drug Advances to Phase II Human Trials

For generations, the loss of a permanent tooth has been an irreversible biological event. Modern dentistry has engineered remarkable artificial workarounds—titanium implants, porcelain crowns, and removable dentures—but a true biological replacement has remained science fiction. Now, a Japanese biotechnology startup is advancing clinical trials for a drug that could fundamentally rewrite the rules of human dental care, aiming to stimulate the body to grow a "third set" of natural teeth.[2][3]

The experimental drug, known as TRG035, is being developed by Toregem BioPharma, a spin-off from Kyoto University. Following a successful Phase I safety trial in adult men, the company recently secured $5.3 million in new funding to launch Phase II trials. This next crucial phase will test the drug's efficacy in its primary target demographic: young children suffering from severe congenital hypodontia, a rare genetic condition that leaves them missing six or more permanent teeth from birth.[1][2]

To understand how TRG035 works, researchers had to look closely at the molecular brakes the human body applies to tooth development. Humans naturally grow two sets of teeth—deciduous (baby) teeth and permanent adult teeth. However, scientists have long known that humans also possess tiny, dormant "tooth buds" deep within the jaw. These vestigial structures have the potential to form a third set of teeth, but they are kept permanently inactive by a specific protein.[3][5]

That protein is called Uterine Sensitization-Associated Gene-1, or USAG-1. It acts as a biological off-switch, suppressing the activity of Bone Morphogenetic Protein (BMP) and Wnt signaling—two critical molecular pathways that drive bone and tooth formation. As long as USAG-1 is active, the dormant tooth buds cannot develop, ensuring that humans do not continuously grow new teeth like sharks or certain reptiles.[4][5]

TRG035 is a monoclonal antibody designed specifically to neutralize this barrier. By binding to and blocking the USAG-1 protein, the drug effectively removes the brakes on tooth development. Once the suppression is lifted, BMP signaling can resume, theoretically signaling the dormant tooth buds to wake up and begin the complex process of forming a new, natural tooth.[1][4]

The foundational research behind this mechanism was led by Dr. Katsu Takahashi, head of dentistry and oral surgery at the Medical Research Institute Kitano Hospital. In a landmark 2021 study published in Science Advances, Takahashi's team demonstrated that administering the anti-USAG-1 antibody to mice with congenital tooth agenesis successfully stimulated the growth of missing teeth.[3][4]

Crucially, the researchers subsequently tested the antibody on ferrets. Unlike mice, ferrets are diphyodonts—meaning they naturally grow two sets of teeth over their lifespan, making their dental patterns highly similar to humans. The treatment successfully induced the growth of a third set of teeth in the ferrets without causing severe systemic side effects, paving the way for human trials.[3][4]

The transition to human testing began in late 2024 at Kyoto University Hospital. The Phase I trial enrolled 30 healthy adult men, aged 30 to 64, who were missing at least one molar. Because this initial phase was designed strictly to evaluate the drug's safety and tolerability rather than its ability to regrow teeth in adults, the operational conclusion of the trial in early 2026 without serious adverse events marked a major green light for the research team.[2][3]

The upcoming Phase II trial represents the true test of efficacy. It will focus on children aged 2 to 7 who have congenital hypodontia. For these pediatric patients, the clinical stakes are incredibly high. Because a child's jawbone is still actively growing and developing, permanent titanium implants cannot be safely placed until they reach adulthood.[1][2][5]

As a result, children missing multiple teeth are often forced to rely on removable dentures for years. This can lead to severe difficulties with chewing and nutrition, impaired speech development, and significant social stigma. If TRG035 can successfully trigger the growth of their missing teeth, it would offer a permanent, biological cure rather than a decade of stopgap management.[1][2][5]

While the immediate focus is on congenital conditions, Toregem BioPharma has made no secret of its ultimate ambition: treating acquired tooth loss in adults. The company hopes that by 2030, the drug could be commercially available and eventually adapted for the millions of people who lose teeth to severe decay, periodontal disease, or traumatic injury.[1][2][3]

In aging populations, such as Japan's, where a vast majority of seniors are missing at least one tooth, a biological replacement could drastically improve nutritional intake and overall longevity. However, independent dental experts urge caution regarding this broader application. Some researchers point out that while children possess abundant dental epithelial cells necessary for tooth formation, adults who have been missing teeth for years may lack the foundational cellular architecture required for the drug to work.[3][5]

Furthermore, precisely controlling the growth—ensuring that the new tooth emerges in the correct location, with the correct shape, and without triggering unwanted bone growth elsewhere—remains a formidable clinical challenge. The Phase II trials will provide the first real evidence of whether the human body can be safely coaxed into executing this complex biological program on demand.[3][5]

Despite these hurdles, the sheer possibility of a "teething medicine" represents a paradigm shift in regenerative medicine. For decades, dentistry has been defined by extraction and artificial substitution. If the anti-USAG-1 antibody proves successful, it will mark the dawn of an era where the body is given the tools to repair its own smile.[1][3][5]